Plants Perform "Green Clean" of Toxic Sites

Brian Handwerkfor National Geographic News

September 24, 2004

Many plants employ natural processes to clean contaminated soil and groundwater. One such process is phytoremediation, by which plants remove heavy metals, such as mercury and lead, from soil. Researchers are now helping plants do a quicker, better job of rehabilitating polluted sites through phytoremediation.

Guy R. Lanza is a microbiology professor and director of the environmental sciences program at the University of Massachusetts in Amherst.

Among other projects, Lanza studies how phytoremediation technology can be applied to New England's Blackstone River corridor, an early birthplace of the U.S. industrial revolution.

Hundreds of years of pollution have left riverside sites in Massachusetts and Rhode Island contaminated with what Lanza dubs "a complicated chemical soup." Conventional cleanup methods of excavating and removing toxic silt and soil are not practicalthe contamination zone is simply too enormous.

Taking a cue from nature, Lanza and his colleagues visited a contaminated pond and studied the wetland vegetation surviving that environment.

"We're trying to isolate, and hopefully manipulate, the plant systems to do more of what we want them to do," Lanza said. "In this case to remove these toxic metals." The researcher said his investigation shows that removing heavy metals like lead, cadmium, zinc, and arsenic with plants is feasible.

Industrial Legacy

At Ford Motor Company's Rouge Center in Dearborn, Michigan, decades of steelmaking left soil contaminated with highly carcinogenic compounds known as polycyclic aromatic hydrocarbons, or PAHs.

With funding from the automaker, Michigan State University researcher Clayton Rugh and University of Michigan-Dearborn researcher John Thomas developed a phytoremediation cleanup system. Their approach used native plants, which also boosted a sitewide initiative to restore the facility's native wildlife habitat.

The project is now in its fourth summer.

Rugh said ten plant species were the standout performers, among them New England aster, joe-pye weed, and leadplant.